As is known, components made of ceramic material of a monolithic type, for example, made of silicon carbide or silicon nitride, have a high mechanical resistance and good resistance to thermal fatigue, but are relatively brittle and do not tolerate sharp thermal gradients. To overcome said drawback, in the last few years the trend has been to produce composite materials having a ceramic matrix and reinforcements made of ceramic fibres. In this type of materials, it is advantageous to coat the surface of the fibres with a material that is heterogeneous both with respect to the matrix and with respect to the fibres so as to increase the toughness by means of the mechanism of deflection of propagation of the crack from perpendicular to parallel with respect to the surface of interface between the matrix and the fibres, at the same time guaranteeing an adequate transfer of the loads.
In addition, there has been asserted the trend to use ceramic oxides in so far as non-oxide materials do not present a good resistance to oxidation at high temperatures (for example, temperatures of approximately 1250° C.) and are subject to creep phenomena and phenomena of corrosion due to aggressive environments.
Unfortunately, the known production processes for making composite materials with a ceramic matrix and a base of ceramic oxides entail long times and high costs.
The U.S. patent application No. US 2006-0280940 A1 describes a production method that should enable reduction of the production times and, simultaneously, obtaining components with satisfactory mechanical characteristics. Such production process comprises the steps of: preparing a suspension of fluid and pourable ceramic powders; impregnating continuous fibres made of ceramic oxide using said suspension; using the impregnated fibres for forming a body made of non-sintered composite material, referred to as “green body”; eliminating the water from the green body via drying; and finally sintering the green body.
However, also this production process proves unsatisfactory in so far as the obtained composites have very high values of porosity (comprised between 45% and 75%).